Display converter for recording multiplicity of oscilloscope traces

ABSTRACT

An oscilloscope, serving to display the traces of different output voltages of a test circuit representing at least two circuit parameters (amplitude and phase) in various testfrequency bands, is coupled to a graphic recorder through a converter including a source of triangular sweep voltage for the x-deflection of the stylus of the recorder. The cadence of this sweep voltage is substantially lower than that of a triangular scanning voltage (wobble frequency) serving for the exploration of each band, a comprator in the converter generating a coincidence signal upon detecting a match between the two triangular frequencies to pass a sample of the output voltage for deflecting the stylus in the y-direction. Whenever the monotonically varying sweep voltage over- or undershoots the range of the scanning voltage derived from the oscilloscope input, the prolonged absence of the coincidence signal gives rise in the converter to an end-of-sweep signal which, upon every third occurrence, causes a switchover to a different parameter and/or frequency band. The switchover in the oscilloscope input is accompanied by a modification of the basic horizontal and/or vertical control voltage for the stylus so that the new trace is inscribed on a different portion of the paper sheet serving as a recording medium. Each recording cycle includes a high-speed first period for the registration of an upper reference line, a low-speed second period for the inscription of the trace and a high-speed third period for the registration of a lower reference line.

United States Patent [1 1 Volkmann et al.

[ Sept. 25, 1973 DISPLAY CONVERTER FOR RECORDING MULTIPLICITY OFOSCILLOSCOPE TRACES [75] Inventors: Klaus Volkmann, Reutlingen-Sodelfingen; Rudolf Dick, Eningen u.a.. both of Germany [73] Assignee:Wandel u. Goltermann K.G.,

Muhleweg, Germany [22] Filed: Sept. 11, 1972 [21] Appl. No.: 288,097

[30] Foreign Application Priority Data Sept. 9, 1971 Germany P 2l 45034.0

[52] U.S. Cl 346/33 R, 346/29, 346/23 [51] lnt. Cl. G01d 5/00 [58] Fieldof Search 346/33 R, 33 A, 17, 346/29, 23,44

[56] References Cited UNITED STATES PATENTS 2.895.784 7/1959 Rocha346/33 EC 3.0011547 9/l96l Kerns 346/33 A [57] ABSTRACT An oscilloscope,serving to display the traces of different output voltages of a testcircuit representing at least two circuit parameters (amplitude andphase) in various test-frequency bands, is coupled to a graphic recorder through a converter including a source of triangular sweepvoltage for the x-deflection of the stylus of the recorder. The cadenceof this sweep voltage is substantially lower than that of a triangularscanning voltage (wobble frequency) serving for the exploration of eachband, a comprator in the converter generating a coincidence signal upondetecting a match between the two triangular frequencies to pass asample of the output voltage for deflecting the stylus in they-direction. Whenever the monotonically varying sweep voltage overorundershoots the range of the scanning voltage derived from theoscilloscope input, the prolonged absence of the coincidence signalgives rise in the converter to an end-of-sweep signal which, upon everythird occurrence, causes a switchover to a different parameter and/orfrequency band. The switchover in the oscilloscope input is accompaniedby a modification of the basic horizontal and/or vertical controlvoltage for the stylus so that the new trace is inscribed on a differentportion of the paper sheet serving as a recording medium. Each recordingcycle includes a high-speed first period for the registration of anupper reference line, a low-speed second period for the inscription ofthe trace and a high-speed third period for the registration of a lowerreference line.

18 Claims, 3 Drawing Figures GRAPIUL STORAGE RHONDER Patented Sept. 25,1973 3,761,947

5 Sheets-Sheet 2 Patented Sept. 25, 11973 3,7Mfi%? 3 Sheets-Sheet 5 F lG. 3 f 202 9%. f, o I V DISPLAY CONVERTER FOR RECORDING MULTIPLICITY OFOSCILLOSCOPE TRACES FIELD OF THE INVENTION Our present invention relatesto a display converter designed to make a permanent record of traceselectronically projected upon a screen of a cathode-ray tube.

BACKGROUND OF THE INVENTION A conventional display converter of thischaracter, described in a brochure entitled CRT DISPLAY CON- VERTERS andpublished by Pacific Measurements Incorporated of Palo Alto, CA with theidentification PM ll-l005-7-69, comprises a graphic recorder having twoconjugate inputs for displacing a writing implement such as a pen or astylus across a recording medium such as a strip of graph paper. Oneinput of the recorder, which for reference purposes may be termed thehorizontal or x input, receives a periodic sweep voltage whose frequencyis low compared with the frequency of the oscilloscope scan in the samedirection; thus, the beam of the cathode-ray tube sweeps many timeshorizontally across the oscilloscope screen while the pen executes asingle stroke across the assigned writing area of the graph paper.Whenever the two sweep voltages bear a predetermined relationshipindicating that the beam and the pen are in corresponding positionsalong the abscissa (in terms of fractions of the overall stroke) withreference to the origin of the co-ordin'ate system, a comparator opens asampling gate to supply to the vertical or y" input of the recorder asignal proportional to the vertical deflection of the beam, therebyplacing the pen of the recorder in a corresponding position along theordinate. In this way, in a succession of coincidences of the xpositions of the beam and the pen, a recurrent trace seeminglystationary on the oscilloscope screen is faithfully reproduced on therecording medium with a degree of resolution depending upon the ratio ofthe two horizontal sweeps.

OBJECTS OF THE INVENTION The general object of our present invention isto provide a system of this type enabling the recording, in rapidsuccession, of two or more traces resulting from modifications of theoscilloscope input.

A more specific object is to provide a system in which the traces to berecorded represent measurements of certain parameters of a transmissioncircuit or test pad,

such as attenuation and/or phase angle, as determined in a number offrequency ranges.

SUMMARY OF THE INVENTION These objects are realized, pursuant to ourpresent invention, by including a supply of supplemental voltage in atleast one of the two conjugate input circuits of the aforedescribedrecorder whereby the writing implement can be shifted (horizontallyand/or vertically) to a plurality of different areas of the recordingmedium, this shifting taking place concurrently with a switchover at thesignal source feeding the verticaldeflection circuit of the cathode-raytube. Naturally, the supplemental voltage producing the shift should belarger than the maximum voltage excursion'in the corresponding direction(x or y) during inscription of a single trace; thus, a number of suchtraces can be recorded in the assigned areas side by side and/or oneabove the other.

In accordance with a more particular object of our invention, thelow-frequency sweep voltage applied to the horizontal recorder input isallowed to vary in a monotonic manner, i.e., to increase or decreaseprogressively, beyond the point which corresponds to the limit of thehorizontal beam sweep whereupon no further coincidences can be detectedby the comparator; the prolonged absence of coincidence signals from thecomparator output empties a storage circuit of integrating character andgives rise to an end-of-sweep pulse. This end-of-sweep pulse may alertthe operator to the fact that a trace has been fully recorded and thatthe switchover in the oscilloscope input and the activation (ordeactivation) of the supplemental-voltage supply in the recorder inputcan take place to shift the writing implement to a different recordingarea. In the preferred embodiment described hereinafter, in which thesystem is fully automated, this switchover and shifting is carried outby a programmer in response to the end-of-sweep signal; in that case, areversing input of the sweep-voltage generator is triggered to alternatebetween increasing and decreasing sweep voltages in response tosuccessive end-of-sweep pulses.

If the recording medium is a graph paper and if the recorder is properlycalibrated, the value of the deflecting voltage at each point of theinscribed curve may be determined directly from the magnitude of theordinate. Since these conditions are not invariably fulfilled, anadvantageous feature of our invention provides for the application of apredetermined reference voltage to the vertical recorder inputin lieu ofa driving voltage derived from the vertical-sweep circuit of theoscilloscope-during certain intervals referred to hereinafter as OFFperiods, in contradistinction to the ON periods in which a projectedtrace is being reproduced. In these OFF periods, therefore, the constantreference voltage holds the writing implement at a fixed distance fromthe abscissa to register a horizontal line, preferably across the entirewriting area reserved for the associated trace; a lower and an uppervoltage limit may be registered in this manner with the aid of twoconstant reference voltages during different OFF periods.

Thus, the numbers n of horizontal pen strokes between switchovers mayvary between 1 and 3, depending on whether no, one or two referencelines are to be recorded along with the trace; in principle, of course,n could also be larger. In a three-stroke switching cycle, the firstend-of-sweep pulse (or the actuation of a start switch at the beginningof operations) introduces a first OFF period during which thelow-frequency sweep voltage at the x input of the recorder variesmonotonically in one sense, e.g., with ascending slope, across theentire sweep range for inscribing one of the two reference levels; theend of the first OFF period is marked by the next end-of-sweep pulse andcoincides with the beginning of an ON period during which the trace onthe oscilloscope screen is recorded by a reverse sweep of the pen. Afurther end-of-sweep pulse terminates the ON period and initiates asecond OFF period during which the second reference level is inscribed,the pen again moving in the original forward direction. A certaininterval must now be provided to permit the transport of the pen to itsnext writing area, advantageously with a return of the sweep voltage tothe value it had at the start of the cycle so that the direction of penmotion in the three periods of the next cycle is the same as before.

After every nth end-of-weep pulse, therefore, a counter in theprogrammer emits a stop pulse to shift the pen and to switch frequencyand/or parameters in the oscilloscope input. If the display converter isto be used in a system for measuring attenuation and phase angles in atest pad, e.g., as described in commonly owned US. Pat. No. 3,584,295,the oscilloscope input may be alternately switched by successive stoppulses to the outputs of an attenuation indicator and a phase meter withsimultaneous shifting of the pen so that the attenuation curves arerecorded on one side and the phase curves are recorded on the other sideof the paper; after every two (or, more generally) m) stop pulses, avertical shift takes place with selection of a new band of testfrequencies, this procedure being repeated p times for as many frequencybands to fill an array of m-p writing areas on the recording medium.

Advantageously, as known per se from the publication cited above, therecorder is provided with an ancillary (pen-lift) input whoseenergization removes the writing implement from the recording medium toavoid unnecessary and confusing markings. In our present system, theprogrammeradvantageously maintains this ancillary input energized notonly in the short intervals of sweep reversal beyond the range limitsbut also dur ing the fly-back stroke of the sweep voltage after thesecond OFF period, thus at the time when the pen is shifted to itsstarting point on the next-following writing area. This fly-back strokemay be of shorter duration (i.e., of larger absolute slope) than theforward strokes during the OFF periods which in turn are advantageouslymuch shorter than the return stroke during the ON period; since therecording of a horizontal reference line does not require any degree ofresolution, the acceleration of the sweep during these forward strokessaves time without sacrificing any information.

According to another feature of our invention, the' sampling gate in thedriving circuit for the vertical recorder input has an operating leadincluding an ancillary switch which is controlled by the programmer tomake the closure of this gate independent of the occurrence ornonoccurrence of coincidence signals from the comparator during the OFFperiods. For this purpose, the operating lead of the sampling gate isconnected during each OFF period by the ancillary switch to a source ofconstant-cadence pulses which may be derived from the horizontal sweepvoltage of the oscilloscope, e.g., through a differentiation circuit.With the sampling gate opening and closing in rapid succession, eitherperiodically during OFF period or aperiodically (in response to thecoincidence signals) during ON periods, the pulses traversing this gateare received in an accumulating network which may be an R/C integratorsimilar to the aforementioned storage circuit for the coincidencesignals) and whose time constant is preferably adjustable for mosteffective noise suppression. While the periodic sampling of anidentically recurring signal has the effect of filtering some of theaccompanying noise, additional noise suppression may be obtained byincreasing this time constant to reduce the bandwidth. On the otherhand, a reduction in the sweep frequency of the recorder increases thenumber of coincidence during a pen stroke and therefore enhances thedegree of resolution, thereby further improving the signal-to-noiseratio. As this latter measure increases the bandwidth, the adjustment ofthe sweep frequency and that of the time constant of the accumulatingnetwork may be carried out simultaneously with opposite effects upon thebandwidth. Any such variation of the time constant of the accumulatingnetwork necessarily affects the relative magnitude of the input andoutput voltages of that network; since, however, the reference voltagespass through the same accumulator, the calibration of the record on thebasis of the inscribed reference levels remains correct.

BRIEF DESCRIPTION OF THE DRAWING The above and other features of ourinvention will now be described in detail with reference to theaccompanying drawing in which:

FIG, 1 is a circuit diagram of a display and recording system embodyingour invention;

FIG. 2 is a set of graphs relating to the operation of the system ofFIG. 1; and

FIG. 3 illustrates a permanent record of attenuation and phase anglesfor different test frequencies as obtained from the system of FIG. 1.

SPECIFIC DESCRIPTION FIG. 1 shows an oscilloscope 1 and a graphicrecorder 2 interconnected by a display converter accord' ing to ourinvention; the elements of this converter could be convenientlyaccommodated in a common housing to form a module which can be connectedto respective terminals of the oscilloscope and the recorder withoutrequiring internal changes in either of them.

Oscilloscope 1 comprises a conventional cathode-ray tube with horizontaland vertical deflecting electrodes 101, 102. Electrode 101 isperiodically energized from a sweep circuit 103 with a triangularscanning voltage U of relatively high frequencyf under the control of awobble-frequency oscillator 104 also feeding a frequency modulator 105.An oscillator 106, generating a test frequencyf, which is variable insteps, works into the modulator 105 to produce a frequency-modulatedoscillation traversing a test pad 107. The amplitudes of thisoscillation at the input and the output of pad 107 are compared in adetector 108 measuring the attenuation introduced by the pad; in ananalogous manner, a discriminator 109 determines the phase shiftundergone by the test oscillation on its passage through the pad 107. Aswitch 110 alternately connects the output of test pad 107 to detector108 and phase discriminator 109. Networks 108 and 109 constitute thesource of a deflecting signal U applied to electrode 102.

The elements so far described are entirely conventional, as is a sweepcircuit 12 which generates a triangular voltage 14, of a frequencysubstantially lower than wobble frequncy f giving rise to thehorizontalsweep voltage U A potentiometer 111 derives from the output ofsweep generator 103 a fraction u of scanning voltage U and feeds it viaa leed 8 to one input of a comparator receiving the low-frequency sweepvoltage u from generator 12 on its other input. As shown in the topgraph of FIG. 2, comparator 9 ascertains the points of intersection P ofthe two voltage curves u and u to generate a succession of coincidencesignal u (FIG. 2, second graph) whenever the voltage u lies within theswing range of voltage u In practice, the ratio of the two sweepfrequencies is much higher than has been illustrated, for convenience,

in FIG. 2. Furthermore, the sweep voltage u, need not rise and falllinearly, as shown, but could follow a somewhat curved path withoutmaterially affecting the operation of the system.

Signals u pass through a shaping circuit 9a deriving a succession ofshort voltage pulses U, (third graph of FIG. 2) from their descendingflanks, these pulses U, occurring only in the wake of coincidences Pbetween curve 14,, and negative-slope portions of curve u Pulses U, areapplied to one input (diagrammatically shown as a bank contact) of anancillary switch 11 whose other input receives the output Au of thedifferentiation circuit connected to lead 8; this output Au is a pulsetrain of constant cadence, coinciding with the descending flanks ofvoltage u as illustrated in the sixth graph of FIG. 2. Pulses U, arealso delivered to a storage circuit 22 which includes a flip-flop, notshown, whose binary output U (fourth graph of FIG. 2) is of finitemagnitude (here positive) whenever the pulses U, follow one another inrapid succession but goes to zero as soon as these pulses disappear fora small number of cycles of voltage 14,, as determined by the timeconstant of the integrating part of storage circuit 22 ahead of itsflip-flop. Thus, the absence of an output from storage circuit 22indicates that the lowfrequency sweep voltage u has either overshot orundershot the high-frequency sweep voltage u Through an inverting inputof an OR gate 23, voltage U,,,, is also applied to ancillary input 103of recorder 2 so that the pen-lifting magnet thereof operates wheneverthe sweep voltage u is out of range.

The switch 11, which like all the other switches here dislosed is of theelectronic type, is connected to a control input of an electronicsampling gate 7 included in a pen-drivingcircuit which extends betweenoscilloscope electrode 102 and recorder input 17. This driving circuitincludes a potentiometer 112 deriving from the deflecting voltage U aproportional fraction u fed to gate 7 through a switch 5 of a modeselector 3. Two other switches 4 and 6 of this mode selector may bealternately closed, in lieu of switch 5, to deliver either of two fixedreference voltages U (high) and U (low) to the gate 7. The voltages U uand U have been illustrated in the three bottom graphs of FIG. 2.

Switches 4, 5 and 6 are controlled by a programmer 16 in response to theoutput signal U of storage circuit 22, the programmer having a startswitch 16a such as a pushbutton which can be manually closed for aninstant to initiate the sequence of operations described hereinafter.Pulse train Au from differentiator 10 is also supplied to programmer 16for timing the output pulses of the programmer to coincide with or startat the negative flanks of sweep voltage u Programmer 16 has three outputleads 3], 32, 33 respectively controlling the switches 4, 5, and 6 ofmode selector 3 which operate in successive periods t t and t fol lowedby a fly-back period t as shown at the bottom of FIG. 2. Leads 31-33also extend to sweep generator 12 to modify the slope of its outputvoltage; thus, as likewise shown in FIG. 2, curve 14,, has a largepositive slope during OFF periods t and a small negative slope during ONperiod t,,, traversing the swing range of voltage u in a relativelyshort time t on the upstroke and in a relatively long time t" on thedownstroke. At the end of each of these periods the programmer 16 emitsa reversing command U (seventh graph of FIG. 2) in the form of a shortend-of-sweep pulse on a lead 34 extending to switch 11 and sweepgenerator 12; thus, switch 11 stands on its right-hand input duringperiods I t of rising sweep voltage and on its left-hand input duringperiods t of falling sweep voltage. During period t however, programmer16 energizes an output lead 35 terminating at OR gate 23 so as tomaintain the recorder pen 201 in its inoperative position. The pen-liftsignal U on lead 103 has been illustrated in the fifth graph of FIG. 2.

The end-of-sweep pulses U,, are applied within the programmer 16 to apulse counter 16 which, upon every third of these pulses, generates astop pulse U (eighth graph of FIG. 2) on a lead 36 terminating at aswitch 15, the latter switch being ganged with the switch 110 in theoutput of test pad 107. Switch 15 has an output lead 37 terminating at asumming circuit 13 also receiving, via a lead 38, the sweep voltage ufrom generator 12; circuit 13 works into input 14 of recorder 2. In theillustrated starting position of switches 15 and 110, in which thedeflecting voltage U,,,,, for oscilloscope 1 is obtained from phasediscriminator 109, lead 37 is grounded so that the output voltage U ofsumming circuit 13 is identical with its input voltage u thus, asillustrated in FIG. 3, the phase angle Aqb is traced in the left-handhalf of recording paper 202. In the alternate switch position, in whichthe detector 108 feeds the deflecting electrode 102, a fixedsupplemental voltage from a battery 15a on lead 37 is superimposed inthe summer 13 upon the sweep voltage a to shift the pen to theright-hand half of the paper for recordal of the attenuation AV/V.Summing circuit 13 and switch 15 together constitute, therefore, avoltage modifier in the horizontal input of recorder 2.

Another summing circuit 18 is inserted between the sampling gate 7 andthe vertical input 17 of recorder 2. An accumulating network 19 withadjustable time constant, comprising a series resistor R and a shuntcapacitor C, filters high-frequency noise from the signal u during ONperiods t and, as shown, may be ganged with sweep generator 12 for jointadjustment in the manner described above. Through an isolating amplifier19a, network 19 feeds one input of summer 18 whose other input isconnected via a lead 39 to a supplemental-voltage source 20. This sourcecomprises a potentiometer 21, connected across a d-c supply 21a, whichis adjustable in steps jointly with test-frequency oscillator 106 so asto impress upon lead 39 a stepped voltage whose steps coincide with theselection of different test frequencies f,. The separation of theseseveral test frequenciesfl, which in FIG. 3 have been designatedf f,,may be approximately equal to the frequency excursion introduced bymodulator so that successive frequency bands follow one another withlittle or no overlap. The voltage steps produced by potentiometer 21are, of course, larger than the maximum swing of signal voltage u,,,,.as modified by accumulator 19 and amplifier 19a. Thus, summer 18produces an output voltage U,,, which causes a vertical shift of pen 201by a height of one row of the array of FIG. 3; together with source 20,this circuit constitutes a voltage modifier for the vertical recorderinput.

The switchover from one frequency f, to the other with concurrentadjustment of potentiometer 21 is carried out by a pulse U emitted bythe programmer 16 on a lead 40 upon the occurrence of every other stoppulse U The ninth, tenth and eleventh graphs of FIG. 2 respectivelyillustrate the supplemental voltage U on lead 37, the stepping pulse Uon lead 40 and part of the supplemental voltage U on lead 39.

Programmer 16 may be so wired that, as illustrated in FIG. 3, the briefclosure of start switch 16a establishes a position in whichmode-selector switch 4 is open, sweep generator 12 produces a minimumoutput voltage (e.g., zero) and supplemental-voltage sources 15 andground the leads 37 and 39, respectively. With successive switchoversunder the control of pulses U and U,,,,, the reference levels U and Utogether with the traces u are recorded on paper 202 in an array ofrectangular areas divided into two columns for parameters Ad) and Av/ vas well as eight rows assigned to test frequencies f, f

In a semi-automatic system of the type described, an operator maymanually perform the various switching functions upon observing thedisappearance of signal U (e.g., as indicated by a monitoring lamp)which marks the end of a sweep.

FIG. 2 also shows that the application of signal u to accumulator 19 atthe beginning of an ON period commences even before the reappearance ofsignal U i.e., while the writing implement 201 is still inoperative, sothat this implement finds itself in the proper position to start tracingas soon as the pen-lift signal U goes to zero.

We claim:

1. A system for making a permanent record of a variety of phenomenatranslatable into periodically recurrent deflecting signals for the beamof a cathode-ray tube, comprising:

a cathode-ray-tube oscilloscope with a horizontalsweep circuit connectedto a source of highfrequency scanning voltage and with averticaldeflection circuit connected to a source of said recurrentsignals, said scanning voltage being synchronized with the recurrencerate of said signals;

a graphic recorder provided with first input means for controlling thehorizontal deflection of a writing implement and with second input meansfor controlling the vertical deflection of said implement across arecording medium;

a generator of low-frequency sweep voltage;

comparison means connected to said generator and to saidhorizontal-sweep circuit for emitting a coincidence signal upon theoccurrence of a predetermined relationship between said high-frequencyscanning voltage and said low-frequency sweep voltage;

first circuit means connected to said generator for applying saidlow-frequency sweep voltage to said first input means;

second circuit means controlled by said comparison means forestablishing a connection between said vertical-deflection circuit andsaid second input means in response to said coincidence signal;

a supply of supplemental voltage in at least one of said circuit meansfor modifying the energization of the associated input means of saidrecorder; and

switchover means operable to alter the output of said source ofrecurrent signals concurrently with modification of the energization ofsaid associated input means for successively inscribing replicas ofdifferent oscilloscope traces on different areas of said recordingmedium.

2. A system as defined in claim 1, further comprising storage means forsaid coincidence signal connected in the output of said comparison meansfor generating an end-of-sweep pulse upon prolonged absence of saidcoincidence signal.

3. A system as defined in claim 2, further comprising programming meanscontrolled by said storage means for actuating said switchover means inresponse to said end-of-sweep pulse, said generator having a reversinginput connected to said programming means for triggering thereby toalternate between increasing and decreasing sweep voltages in responseto successive endof-sweep pulses.

4. A system as defined in claim 3 wherein said programming meansincludes a counter for a predetermined series of n end-of-sweep pulsesseparated by alternating ON and OFF periods, further comprising a sourceof reference voltage and switch means in said second circuit meanscontrolled by said programming means for connecting said source ofreference voltage in lieu of said vertical-deflection circuit to saidsecond input means during OFF periods, said switchover means beingactuatable by a stop pulse from said programming means coinciding withevery n end-of-sweep pulse.

5. A system as defined in claim 4 wherein said supply of supplementalvoltage includes a first voltage modifier in said first circuit meansand a second voltage modifier in said second circuit means, saidprogramming means being effective to step one of said voltage modifiersthrough an m-step cycle of successive stop pulses and to step the otherof said voltage modifiers through a p-step cycle on every m" stop pulsewhereby said writing implement is successively shifted across all theareas of an array ofp-m areas of said recording medium.

6. A system as defined in claim 5 wherein said recurrent signals arederived from a plurality of voltage sources representing differentparameters measured in the output ofa test circuit with any of severalinput frequencies modulated in the rhythm of said highfrequency scanningvoltage, said switchover means selecting n different parametersconcurrently with the stepping of said one of said voltage modifiers andselecting m different input frequencies concurrently with the steppingof said other of said voltage modifiers.

7. A system as defined in claim 5 wherein said voltage modifiers includerespective summing circuits.

8. A system as defined in claim 4 wherein said programming means isprovided with a start switch for initiating the operation thereof in aposition of said switch means connecting said source of referencevoltage to said vertical-deflection circuit.

9. A system as defined in claim 4 wherein said second circuit meansincludes a sampling gate between said switch means and said second inputmeans, said sampling gate being provided with an operating leadextending from said comparison means, and an ancillary switch in saidoperating lead controlled by said programming means for making theclosure of said sampling gate independent of said coincidence signalduring OFF periods.

10. A system as defined in claim 9 wherein said second circuit meansfurther includes an accumulating network for pulses traversing saidsampling gate, said sampling gate being periodically closable during OFFperiods by constant-cadence pulses supplied thereto through saidancillary switch.

111. A system as defined in claim 9, further comprising a connectionbetween said ancillary switch and said source of scanning voltage forderiving said constantcadence pulses from the latter.

12. A system as defined in claim 11 wherein said connection includes adifferentiation network.

13. A system as defined in claim wherein said accumulating networkcomprises an R/C circuit with adjustable time constant.

14. A system as defined in claim 13 wherein said generator of sweepvoltage is adjustable and ganged with said R/C circuit for varying theslope of said sweep voltage inversely with said time constant.

15. A system as defined in claim 4 wherein said counter establishes twoOFF periods separated by one ON period during a series of threeend-of-sweep pulses, with application of different reference voltages tosaid second input means by said switch means during said two OFFperiods, said low-frequency sweep voltage having a slope of one signduring the OFF periods and a slope of the opposite sign during the OFFperiod whereby said implement moves across said recording medium in onedirection during the OFF periods and in the opposite direction duringthe ON period, said stop signal causing a rapid change in the outputvoltage of said generator for quickly shifting said implement to astarting position.

16. A system as defined in claim 15 wherein said recorder has anancillary input connected to said storage means for removing saidimplement from said recording medium upon prolonged absence of saidcoincidence signal.

17. A system as defined in claim 16 wherein said ancillary input isadditionally connected to said programming means for continuousenergization during the shift of said implement to said startingposition.

18. A system as defined in claim 15 wherein the slope of saidlow-frequency sweep voltage is relatively high during the OFF periodsand relatively low during the ON period.

1. A system for making a permanent record of a variety of phenomena translatable into periodically recurrent deflecting signals for the beam of a cathode-ray tube, comprising: a cathode-ray-tube oscilloscope with a horizontal-sweep circuit connected to a source of high-frequency scanning voltage and with a vertical-deflection circuit connected to a source of said recurrent signals, said scanning voltage being synchronized with the recurrence rate of said signals; a graphic recorder provided with first input means for controlling the horizontal deflection of a writing implement and with second input means for controlling the vertical deflection of said implement across a recording medium; a generator of low-frequency sweep voltage; comparison means connected to said generator and to said horizontal-sweep circuit for emitting a coincidence signal upon the occurrence of a predetermined relationship between said high-frequency scanning voltage and said low-frequency sweep voltage; first circuit means connected to said generator for applying said low-frequency sweep voltage to said first input means; second circuit means controlled by said comparison means for establishing a connection between said vertical-deflection circuit and said second input means in response to said coincidence signal; a supply of supplemental voltage in at least one of said circuit means for modifying the energization of the associated input means of said recorder; and switchover means operable to alter the output of said source of recurrent signals concurrently with modification of the energization of said associated input means for successively inscribing replicas of different oscilloscope traces on different areas of said recording medium.
 2. A system as defined in claim 1, further comprising storage means for said coincidence signal connected in the output of said comparison means for generating an end-of-sweep pulse upon prolonged absence of said coincidence signal.
 3. A system as defined in claim 2, further comprising programming means controlled by said storage means for actuating said switchover means in response to said end-of-sweep pulse, said generator having a reversing input connected to said programming means for triggering thereby to alternate between increasing and decreasing sweep voltages in response to successive end-of-sweep pulses.
 4. A system as defined in claim 3 wherein said programming means includes a counter for a predetermined series of n end-of-sweep pulses separated by alternating ON and OFF periods, further comprising a source of reference voltage and switch means in said second circuit means controlled by said programming means for connecting said source of reference voltage in Lieu of said vertical-deflection circuit to said second input means during OFF periods, said switchover means being actuatable by a stop pulse from said programming means coinciding with every nth end-of-sweep pulse.
 5. A system as defined in claim 4 wherein said supply of supplemental voltage includes a first voltage modifier in said first circuit means and a second voltage modifier in said second circuit means, said programming means being effective to step one of said voltage modifiers through an m-step cycle of successive stop pulses and to step the other of said voltage modifiers through a p-step cycle on every mth stop pulse whereby said writing implement is successively shifted across all the areas of an array of p.m areas of said recording medium.
 6. A system as defined in claim 5 wherein said recurrent signals are derived from a plurality of voltage sources representing different parameters measured in the output of a test circuit with any of several input frequencies modulated in the rhythm of said high-frequency scanning voltage, said switchover means selecting n different parameters concurrently with the stepping of said one of said voltage modifiers and selecting m different input frequencies concurrently with the stepping of said other of said voltage modifiers.
 7. A system as defined in claim 5 wherein said voltage modifiers include respective summing circuits.
 8. A system as defined in claim 4 wherein said programming means is provided with a start switch for initiating the operation thereof in a position of said switch means connecting said source of reference voltage to said vertical-deflection circuit.
 9. A system as defined in claim 4 wherein said second circuit means includes a sampling gate between said switch means and said second input means, said sampling gate being provided with an operating lead extending from said comparison means, and an ancillary switch in said operating lead controlled by said programming means for making the closure of said sampling gate independent of said coincidence signal during OFF periods.
 10. A system as defined in claim 9 wherein said second circuit means further includes an accumulating network for pulses traversing said sampling gate, said sampling gate being periodically closable during OFF periods by constant-cadence pulses supplied thereto through said ancillary switch.
 11. A system as defined in claim 9, further comprising a connection between said ancillary switch and said source of scanning voltage for deriving said constant-cadence pulses from the latter.
 12. A system as defined in claim 11 wherein said connection includes a differentiation network.
 13. A system as defined in claim 10 wherein said accumulating network comprises an R/C circuit with adjustable time constant.
 14. A system as defined in claim 13 wherein said generator of sweep voltage is adjustable and ganged with said R/C circuit for varying the slope of said sweep voltage inversely with said time constant.
 15. A system as defined in claim 4 wherein said counter establishes two OFF periods separated by one ON period during a series of three end-of-sweep pulses, with application of different reference voltages to said second input means by said switch means during said two OFF periods, said low-frequency sweep voltage having a slope of one sign during the OFF periods and a slope of the opposite sign during the OFF period whereby said implement moves across said recording medium in one direction during the OFF periods and in the opposite direction during the ON period, said stop signal causing a rapid change in the output voltage of said generator for quickly shifting said implement to a starting position.
 16. A system as defined in claim 15 wherein said recorder has an ancillary input connected to said storage means for removing said implement from said recording medium upon prolonged absence of said coincidence signal.
 17. A syStem as defined in claim 16 wherein said ancillary input is additionally connected to said programming means for continuous energization during the shift of said implement to said starting position.
 18. A system as defined in claim 15 wherein the slope of said low-frequency sweep voltage is relatively high during the OFF periods and relatively low during the ON period. 